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SNARE complex formation is essential for intracellular membrane fusion. Vesicle-associated (v-) SNARE intertwines with target membrane (t-) SNARE to form a coiled coil that bridges two membranes and facilitates fusion. For the SNARE family involved in neuronal communications, complex formation is tightly regulated by the v-SNARE-membrane interactions. However, it was found using EPR that complex formation is spontaneous for a different SNARE family that is involved in protein trafficking in yeast. Further, reconstituted yeast SNAREs promoted membrane fusion, different from the inhibited fusion for reconstituted neuronal SNAREs. The EPR structural analysis showed that none of the coiled-coil residues of yeast v-SNARE is buried in the hydrophobic layer of the membrane, making the entire coiled-coil motif accessible, again different from the deep insertion of the membrane-proximal region of neuronal v-SNARE into the bilayer. Importantly, yeast membrane fusion is constitutively active, while synaptic membrane fusion is regulated, consistent with the present results for two SNARE families. Thus, the v-SNARE-membrane interaction may be a major molecular determinant for regulated versus constitutive membrane fusion in cells. [ABSTRACT FROM AUTHOR]

Examines the usability of the structure of P[sub 11] with adenosine triphosphate. Inclusion of hexagonal crystal form; Emphasis of the level of glutamine synthetase activity; Models for the structures of the heterotrimers.

The C-terminal domain of adenylyltransferase (ATase) from Escherichia coli has been overexpressed, purified and crystallized in a form suitable for structure analysis. The domain is contained in a fragment that extends from residues 441–945 of the intact ATase. [ABSTRACT FROM AUTHOR]